1. Field of the Invention
The present invention relates to a method for forming a capacitor structure. Further, the present invention relates to a capacitor structure in particular a capacitor structure formed on a semi-conductor substrate.
2. Description of the Related Art
The memory capacity of DRAM memory devices per unit area shall be increased for technical and economical reasons. The DRAM memory device comprises a plurality of memory cells. Each of them can store a single information unit in its capacitor. An increase of the memory capacity per unit area can be achieved by reducing the horizontal dimensions, i.e. in the plane of the DRAM memory device, of these capacitors.
For a reliable operation of the memory cells, the electric capacity of the capacitors must be kept above a minimal value. As the electric capacity is proportional to both the vertical and the lateral dimensions, the vertical dimension of the capacitors is increased when horizontal dimensions are reduced. Nowadays, the capacitors have a diameter in the range of 100 nm or less and a height of several micrometers.
A manufacturing process known to the inventor starts by forming a free standing first electrode on a substrate surface. The first electrode has basically the same height as the later formed capacitor, and may have a diameter even less than the capacitor. The mechanical stability of this first electrode is therefore very limited. Thus, some of the first electrode collapse or are deformed before or during the continued manufacturing process.